1. Field of the Invention
The invention relates to a method for generating a pulse train with adjustable start times and end times of individual pulses, in which additional clock signals are generated from a 0th clock signal, the signals which in each case have the frequency of the 0th clock signal and whose phase is shifted in each case relative to the phase of the 0th clock signal.
The invention relates further to a pulse generator, which generates additional clock signals from a 0th clock signal, the signals which in each case have the frequency of the 0th clock signal and whose phase is shifted in each case relative to the phase of the 0th clock signal, and the pulse generator generates a pulse train with adjustable start times and end times of individual pulses of the pulse train from the clock signals.
2. Description of the Background Art
Pulse trains of with different adjustable start times and end times are necessary, for example, as a write pulse sequence for the burning of CDs or DVDs. The times must be adjustable for each pulse in the pulse train with an accuracy of, for example, a 16th or a 64th part of the period duration of a write clock signal. The write clock signal corresponds to a 0th clock signal and has, for example, a period duration of 2.4 ns. In a DVD-R write strategy with 16-fold write speed, for this reason, a grid of 16 steps per clock period of the write clock signal is necessary, which results in a time grid pitch of 150 ps. The edges of the write signal must be adjustable with this time resolution.
In principle, such a time resolution can be provided by multiplexer structures with the aforementioned method features and circuit features. Multiplexer structures of this type supply M signals, generated from a write clock signal, to an output circuit. For this purpose, several multiplexers are necessary, because multiple changes in the output signal may be necessary during a period of the write clock signal. Disadvantages of the multiplexer structure are that a blocking time is necessary to switch the multiplexers, and the circuit functions asynchronously and requires a downstream output stage, which turns the pulses on and off with the different selected signals. Moreover, additional runtime optimization of the signals within the multiplexers and output circuit is necessary. If several pulses are to be generated within a clock period, a costly circuit is necessary. Furthermore, a collision strategy is necessary, if two or more pulses are to superimpose within a clock period.